Biomedical subjects

Heather Carnahan

Publications and source records attributed to Heather Carnahan.

9 recordsLinked to original sources

PubMed2006

Tensiometry as a measure of improvement in knot quality in undergraduate medical students.

INTRODUCTION: This study examined the validity of tensiometry as an objective method of assessing the improvements in the quality of knots and technical performance due to practice on suturing and knot-tying skills. METHODS: We evaluated the quality of 1,830 knots produced by undergraduate medical students before training (pre-test), after (post-test), and after a week retention (retention-test) using tensiometry. These results were compared to expert-based assessments of products and performance. RESULTS: Tensiometry, as well as expert-based assessments can detect changes in the quality of knots and technical performance from pre to post and retention-test ( p<0.05). However, these three methods may assess different dimensions of the same products and actions. CONCLUSIONS: The development of trainee evaluation criteria for the acquisition of surgical skills is a crucial element in surgical education. Based on our patterns of results it is hypothesized that tensiometry can serve as an economic first approximation of the quality of knots and suturing performance.

Analysis of Variance↗

PubMed2006

Control of laparoscopic instrument motion in an inanimate bench model: implications for the training and the evaluation of technical skills.

Computer-assisted analysis of wrist movement has recently emerged as an objective laparoscopic performance evaluation method. The first purpose of this study was to assess the differences in motion characteristics between the tip of the instrument and the wrist. The second purpose was to describe the control strategies used to move laparoscopic instruments. During a bead transfer task, motions of a laparoscopic needle driver's tip, heel, and the participants' wrist were monitored. Results showed that large amplitude movements were best described by movements of the wrist, and small amplitude movements were evidenced by motions of the instrument tip. Thus, for describing expertise, and for evaluation and feedback, motion of the tip of the laparoscopic instrument should be quantified, in addition to motion of the wrist. The motions of the instrument were controlled by utilizing the flexibility of the skin of the laparoscopic trainer in addition to using the fulcrum, and sliding through the trocar. In order to increase fidelity, virtual reality trainers should simulate the flexibility of the real structures around the insertion of the instrument.

Adult↗

PubMed2005

The influence of practice schedules in the learning of a complex bone-plating surgical task.

BACKGROUND: Practicing surgical tasks on bench models can be arranged in 3 ways: as the entire task, or as individual skills practiced separately in blocked or random order. The issue of the optimal practice schedule for the acquisition of surgical tasks is critical for enhancing training programs. METHOD: An orthopedic bone-plating task was practiced as a whole, or in parts in either a random or a blocked order. Learning was assessed on global ratings, checklists, and final product analysis before, immediately after, and an hour after practice. RESULTS: Checklists, and final product analysis, but not the global ratings showed that practicing the entire task resulted in the most learning, followed by the random practice. Practice of the skills in a blocked order yielded the least amount of learning. CONCLUSIONS: It is recommended that surgical tasks composed of several discrete skills should be practiced as a whole. However, if part practice is necessary, these skills should be arranged in random order to optimize learning.

Analysis of Variance↗

PubMed2005

Quantification of motion characteristics and forces applied to tissues during suturing.

BACKGROUND: The quantification of movement processes describes how a movement is generated. These process measures have been shown to be effective sources of feedback to facilitate motor learning and can thus be applied to teach fundamental technical skills in surgery. The aim of this study was to determine, through detailed analyses, whether specific process measures of hand motions and forces imposed on tissues during suturing were sensitive to (1) practice and (2) levels of surgical expertise. METHODS: Six junior surgical residents (PGY-1) and 7 faculty surgeons were required to perform 20 simulated sutures on an artificial artery model, during which time the performers' hand movements were tracked by electromagnetic markers and the quantity of force they applied was measured by a force platform holding the arterial suturing models. The amount of wrist rotation and peak hand velocity produced during the suturing movement, peak and average forces applied to the tissue, the temporal difference between force and wrist rotation onsets, and the total suturing time were evaluated. RESULTS: Surgeons showed greater wrist rotation, higher average forces, shorter force-rotation initiation times, and shorter suturing times than did junior residents. Only the amount of wrist rotation and the time elapsed between force and wrist rotation onsets improved with practice for the junior group. CONCLUSIONS: Although all 4 variables measured can be used to distinguish between expert and novice performances, only the process measures (wrist rotation and force-rotation initiation time) changed as a result of practice for the junior residents. Thus, these measures can be used to facilitate skills learning by serving as a source of detailed structured feedback to trainees.

Clinical Competence↗

PubMed2005

Unilateral basal ganglia damage causes contralesional force control deficits: a case study.

When grasping to lift an object, the grip force is usually scaled to the mass of the object. However, it has been shown that lifting objects of different sizes but equal masses results in the generation of higher forces for larger compared to smaller objects. The objective of this study was to investigate whether a similar effect is present in an individual (RI) with a unilateral lesion to the basal ganglia (BG). It was hypothesized that if the BG have an influence on the use of visual information in updating of the internal model used to anticipate the forces required for grasping, damage to these structures should result in the inability of RI's contralesional hand to anticipate object mass based on size cues. To test this hypothesis three objects of equal mass but different sizes were grasped and lifted by RI and six control individuals. The forces that were generated during these lifts were quantified. The controls showed the expected increases in peak grip force as object size increased. RI showed no effect of object size for his contralesional hand, but did show force scaling with his ipsilesional hand. In conclusion, RI's BG damage affected the on-line control of grip forces and the inability to integrate visual and tactile information in the programming of finger forces.

Adult↗

PubMed2005

Control of laparoscopic instrument motion in an inanimate bench model: implications for the training and evaluation of technical skills.

Laparoscopic surgery requires new methods of technical competency evaluation, as well as training. The first purpose was to assess the differences in motion characteristics between the tip of the instrument and the wrist. The second purpose was to determine whether similar control strategies are used to move instruments in virtual reality and bench model environments. Surgically naive participants were required to tap a laparoscopic instrument between two targets that differed in size and separation distance. Large amplitude movements were controlled with the movements of the wrist and small amplitude with the wrist and the fingers (p<.001). Participants utilized the flexibility of the skin of the laparoscopic trainer to facilitate their movements. These results suggest that monitoring the motions of the instrument tip is a more precise indication of its motions than are motions of the wrist when movements of small amplitudes are produced. Moreover, in order to increase fidelity, VR trainers should simulate the flexibility of the real structures around the insertion of the instrument.

Canada↗

PubMed2004

Practice effects on the use of visual and haptic cues during grasping.

Mapping of arbitrary color cues onto object properties such as mass can influence the control of fingertip forces. One can view the development of that mapping as a motor learning issue, and its development should therefore be influenced by practice schedule. During an acquisition phase, 24 participants lifted color-cued objects that differed in mass. The masses were presented in either blocked or random orders. A test phase consisted of lifts of a midmass object; on some lifts, the object's mass was unexpectedly changed. The change was either accurately color cued or miscued. Only blocked practice led to visually mediated scaling of fingertip forces to object mass. During the test phase, previous blocked practice resulted in reliance on visual cues, and random practice led to a reliance on haptics (sense of touch). Those findings suggest that the integration of arbitrary color cues and haptic information is dependent on practice conditions.

Adult↗

PubMed2002

Action-perception dissociation in response to target acceleration.

The purpose of this study was to investigate whether information about the acceleration characteristics of a moving target can be used for both action and perception. Also of interest was whether prior movement experience altered perceptual judgements. Participants manually intercepted targets moving with various acceleration, velocity and movement time characteristics. They also made perceptual judgements about the acceleration characteristics of these targets either with or without prior manual interception experience. Results showed that while aiming kinematics were sensitive to the acceleration characteristics of the target, participants were only able to perceptually discriminate the velocity characteristics of target motion, even after performing interceptive actions to the same targets. These results are discussed in terms of a two channel (action-perception) model of visuomotor control.

Acceleration↗

PubMed2001

Magnitude estimation of tangential force applied to the fingerpad.

Prior research on large-fibre skin mechanoreceptors in humans and monkeys has demonstrated their sensitivity to perpendicular skin indentation and to the rate of force application. Although some studies have examined skin afferent responses to stretch, relatively few investigations have examined the neural and perceptual correlates of shear forces applied tangentially to the skin. The present study assessed the ability of human subjects to scale different levels of tangential force applied to the distal pad of the index finger. Subjects were instructed to choose their own magnitude estimation scale. Seven force levels ranging from 0.15 to 0.70 N were delivered randomly at rates of 0.10 N/s, 0.15 N/s or 0.30 N/s. Tangential forces were produced with a smooth metal spatula coated with an adhesive to insure a shear force on the underlying skin without slip. The same procedures were also used to generate skin indentation with normal forces. The results showed that most human subjects were able to scale different magnitudes of both tangential and normal forces applied to the tip of the index finger. The rate of force change did not influence the perception of the applied forces. These results highlight the potentially important role of tangential forces in haptic perception.

Adult↗